An excellent move, preserving the knight and getting ready to open the position with b2-b4. Black's problem is that he has no counterplay. Imagine how Vachier-Lagrave, with such an aggressive style, was feeling without being able to play an active move.
16... d4e2 A bit passive. It would be better to take the knight on d5 or play a6-a5, fixing the queenside. In any case, it1s better to let White exchange knights on d4, so that Black has a passed pawn and the d-file cannot be exploited. 17. d3e2  17... f8f7  18. d1d2  18... d8f8 Not an ideal plan, to say the least. Something went very wrong with Black's opening play.